The present invention is related generally to vacuum chamber applications; and, in particular, to a coupling used to supply an electrical bias voltage to a platen rotating within the chamber to apply a coating to an object.
Vacuum coating chambers are used to apply certain types of coatings, usually thin film coatings, to various objects. The method employed utilizes an electrical bias voltage which is supplied to a plate rotating within the chamber, the voltage being used to generate or maintain a stable plasma. Conventional arrangements for doing this are generally both complex and expensive. Their operation is usually to introduce the voltage into the chamber through a stationary feed connected to a voltage source. The stationary feed is electrically coupled to the rotating plate through copper rings, carbon brushes, and wire mesh or gears, for the transmission of power. Other known arrangements utilize swash plates and flexible couplings. Again, while these other arrangements also succeed in conveying the required bias voltage from an external source to the rotating plate within the vacuum chamber, they are also costly, expensive, and create maintenance issues which limit the time available for use of the chamber.
Accordingly, it would be advantageous to provide a simple and cost effective coupling which provides greater higher reliability in introducing a bias voltage into a vacuum chamber having a rotating plate, but which does not require the complex arrangements currently in use and which require a high level of maintenance.